140 PHYSIOGRAPFIY OF TASMANIA. 



ders which form the terraced show, is greenstone, of which 

 the entire structure of the island also consists, as here and 

 there the same formation projects through the shallow soil. 

 In view of this fact some clue is obtained as to the cause 

 of the terraced formation of the shore. 



The island lies almost in the middle of the strait — about 

 1^ mile wide — which connects the two great water tracts at 

 the north of the lake, namely, the large " North-West 

 Bay " and equally wide " East Bend"; and from all points 

 of the compass, save two — north-east and south-west — 

 it is exposed to the full force of the waves, with several 

 miles of water behind them. The prevailing gales 

 on the lake are from the north-west, south-south-west 

 and south-west, and an extremely violent sea rises 

 with them. After a hard winter, when the ice is 

 from three to five inches thick, it generally brea.ks up 

 during these gales, and drives in huge floes, v^ith great 

 violence, on the shore of the island. It seems, therefore, 

 reasonable to suppose that, during the course of the 

 centuries, the effect of wave and ice pressure has been 

 sufficient to cast up what was formerly a foreshore of 

 scattered stones and boulders into rampart, or terrace, now- 

 existing. Once this began to assume the elevated character 

 of a roughly-formed terrace, there is no doubt that the ice 

 iTiOvement and force of the waives w-ould gradually mould 

 it, little by little, into its present form. The formation of 

 the rampart is equally regular on the south-west and north- 

 west sides, the latter part being somewhat less exposed 

 to heavy weather. Round the whole island, with the 

 exception of the cove or break on the east side, the rock 

 ^:>ank is almost of uniform height. 



As the botany of these high regions is interesting, it may 

 be proper to remark on the vegetation which we found 

 clothing the islet. The surface is practically level, there 

 being a gentle rise from the shore towards the " tors " in 

 the centre. The soil is, for the most part, covered with a 

 dwarf form of the ordinary cattle or '' thatch " grass {i^oa 

 CKS'pidosa), thickly interspersed and patched V7ith the 

 Epacris-like bushes Pultenoea ruhuinhellata, Bechia gun- 

 niana, and Comesferma reUisum. The second of these was 

 in flower at the time of my visit, and gave colour to the 

 sward. We noticed that the dead tussocks of " thatch " 

 grass {Pod) were partly covered with a curious earthy-look- 

 ing deposit lying on them in thick patches, and on closely 

 examining them found, to our surprise, that the covering 

 was a lichen. The grass is killed in the usual way, by cold 

 and age, as in the lowlands on our cattle-runs, and is 



